PCI-X is different from PCI Express?

[joecool85]

I have a dual 2ghz G5 with PCI-X, I thought PCI-X was short for PCI-Express...apparently I'm wrong? Are there any good PCI-X cards out there? Are PCI-X slots ok for regular PCI stuff?

 

[Makosuke]

In a truly sad tech naming botch, they are indeed totally different despite the easily confused names. Calling them PCI-e helps a bit, but not to the average, uninformed consumer ('course, the G5s ain't exactly targeted at the average, uninformed consumer--16GB of EEC RAM isn't what you'd call a consumer motherboard).

Anyway, in your case, there are a number of PCI-X cards available, for example most of the newer Mac compatible SATA (external, internal, or both) cards are PCI-X. Newer plain vanilla PCI cards are also compatible with PCI-X slots, so long as the voltage is ok--look up what is necessary, though most cards will say outright if they're compatible with the G5 (I, for example, have an older eSATA PCI card that works fine in my G5). It will result in a speed hit if it's in one of the two slower slots and you've got a PCI-X card next door, I believe. Something like that, anyway.

 

[joecool85]

Huh. What a bummer. All this time I thought I had PCI-Express lol. And I call myself a computer guy Oh well, silly mistake on my part. Luckily most of the people I talk to have no idea anyway.

 

[realityisterror]

I too knew there was some difference, but I've never understood the technical side of things.

Interestingly, someone must have a use for PCI-X capable machines because it seems Apple is keeping the Dual 2.7GHz...


http://www.apple.com/powermac/pcix.html
http://store.apple.com/1-800-MY-APP...wo/StoreReentry.wo?productLearnMore=M9749LL/A



reality

 

[belvdr]

PCI-X is great for Fibre Channel, dual port GigE connections, and the like.

If you really want PCI Express, looks like you'll have to trade up to one of the new dual core Power Mac systems.

 

[atszyman]

A quick summary

PCI-X is a bus based system not unlike standard PCI and is actually backwards compatible with PCI. PCI busses come in 32 and 64 bit varieties running at 33 or 66MHz. PCI-X is a 64-bit bus that can run up to 133 MHz although that is on a dedicated bus with only one card (there have been proposals for 266 and 533 MHz bus standards as well). A two card system can run at up to 100 MHz but the shared bus will only run as fast as the slowest card on the bus, so if you plug in a high performance PCI-X card and a standard 32/33 PCI card you're going to be running the bus at 1/3 of the capability in your PCI-X card (64-bit and 32-bit do not affect eachother).

PCI Express is the newer serial based standard. PCI Express no longer operates on a shared bus type system, instead everything is a dedicated serial channel and as such is not backwards compatible with any other type of PCI. I believe that the 4x slots have 4 serial channels, 8x 8 serial channels and so on, but I have not done much work with PCI Express, yet.

 

[risc]

...there have been proposals for 266 and 533 MHz bus standards as well...

I work with servers at work with PCI-X 2 or 266 MHz PCI-X so that is definitely available, I haven't seen 533 MHz PCI-X yet though.

 

[slooksterPSV]

Speaking of 16GB of RAM. Imagine when they get the 2GB RAM chips out. 32GB of RAM for Mac OS X. *Drools with delite* - heck you wouldn't need the harddrive for the OS, just load all of it into RAM (like the RAM based hard drives you can purchase - put any type of RAM in it, DDR266, 300, 333, 400, 533, etc.

 

[rock6079]

Speaking of 16GB of RAM. Imagine when they get the 2GB RAM chips out. 32GB of RAM for Mac OS X. *Drools with delite* - heck you wouldn't need the harddrive for the OS, just load all of it into RAM (like the RAM based hard drives you can purchase - put any type of RAM in it, DDR266, 300, 333, 400, 533, etc.

the new G5's have 8 RAM slots. So the 16GB of DDR2 memory is based on using 8x2GB sticks. your dream will become reality when 4GB sticks become available, or they have 16 ram slots, or any combination there of

sorry to spoil your excitement

btw , 16GB of ram is not cheap using the 2GB sticks from apple. if i remember from when i was looking before. its about $13000 for the 16gb from apple

 

[slooksterPSV]

the new G5's have 8 RAM slots. So the 16GB of DDR2 memory is based on using 8x2GB sticks. your dream will become reality when 4GB sticks become available, or they have 16 ram slots, or any combination there of

sorry to spoil your excitement

btw , 16GB of ram is not cheap using the 2GB sticks from apple. if i remember from when i was looking before. its about $13000 for the 16gb from apple

11900 lol , I looked it up. Ok, so yeah when the RAM comes to 4GB (which will be very very very expensive till prices drop - Apple make my dream come true and upgrade the iBook to 1GB RAM standard! lol). Dang. Oh well, I can always dream

 

[matticus008]

PCI Express is the newer serial based standard. PCI Express no longer operates on a shared bus type system, instead everything is a dedicated serial channel and as such is not backwards compatible with any other type of PCI. I believe that the 4x slots have 4 serial channels, 8x 8 serial channels and so on, but I have not done much work with PCI Express, yet.

Good summary. I just have one minor correction/addition. PCI Express is backwards compatible with regular PCI in terms of software design (drivers, OS level support) unlike PCI-X. This means that you can continue using the same actual hardware (as a manufacturer, not a consumer) and just repackage it for the PCI Express connections and the new voltage/communication requirements. There was talk of keeping one of the slots hardware-compatible with then-standard PCI 2.1, but I believe that was abandoned. PCIe x16 (the intended replacement for AGP) has up to 16GB/sec bandwidth, which goes down in powers of 2 to PCIe x1 (250MB/sec).

You can tell the cards apart by their connectors, with the x1 being the smallest and the x16 being the biggest. The PCIe x8 connector is roughly the same size as the standard PCI 2.2 slot. You can use any PCIe card in its designated slot or in a bigger one (but you cannot move the card down to a slower slot). This means that video cards will be stuck at x16, but a sound card for x1 can be placed in any open slots of type {x1, x4, x8}...or even an x16 slot if there is one free.

 

[simie]

Here is an overview by ars technica

http://arstechnica.com/articles/paedia/hardware/pcie.ars/1

and

http://www.interfacebus.com/Design_Connector_PCI_Express.html

 

[GFLPraxis]

PCI-X is PCI on steroids- a faster PCI slot.


PCIe is a completely new slot that is even better than PCI-X but not backwards compatible. Most PC's with PCIe use it to replace the AGP slot.

 

[Makosuke]

Thanks for all the concice, informative summaries. Suppose this'll lead to some new PCI-e cards being released in the near future, though it'll probably be a while before all the stuff folks want catch up to the new PMs.

 

[pianojoe]

Last year, my G5 lost its USB-ports. Not wanting to replace the motherboard, I started looking for a PCI-X compatible USB-2.0 PCI-Card. I tried many that didn't work due to voltage differences. Finally, I got one from Sonnet that actually worked.

 

[Harthansen]

Never buy memory from apple

the new G5's have 8 RAM slots. So the 16GB of DDR2 memory is based on using 8x2GB sticks. your dream will become reality when 4GB sticks become available, or they have 16 ram slots, or any combination there of

sorry to spoil your excitement

btw , 16GB of ram is not cheap using the 2GB sticks from apple. if i remember from when i was looking before. its about $13000 for the 16gb from apple

Yeah and about $3000 for 8x2gb ECC-DDR2 533 from everywhere else
Apple memory is now and always has been a rip off. You would think they would at least have high cas latencies. they don't usually 4's and 5's, for the high size chips. NEVER buy ram from apple. Crucial is much better, and they good inexpensive ram as well as expensive ram with low cas and metal heat spreaders. Apple's $1500 a stick 2gb ram has none of that and is still more expensive then crucials highest cost 2gb stick of $800. You can get ecc cas 4 DDR2 533 Mhz 2gb ram for $400-$500 which is what apple sells for $1500.

-HH

 

[Breadfiend]

Audio Interfaces etc.

The people who still need PCI-X are people who want to be able to use things like the RME Hammerfall Audio Interface. Third party audio manufacturers do not as yet support PCI Express (I guess because they weren't told in advance).
I think this a kick in the teeth for the music production types who have been one of Apple's most loyal markets for YEARS. I think the same applies for video capture cards like the Kona range - what's the use of changing the system if you don't let the third party developers in on it?

 

[joecool85]

Wow, all very interesting information. Thanks for all the responses. I guess I wasn't the only one in the dark though.

 

[Harthansen]

The people who still need PCI-X are people who want to be able to use things like the RME Hammerfall Audio Interface. Third party audio manufacturers do not as yet support PCI Express (I guess because they weren't told in advance).
I think this a kick in the teeth for the music production types who have been one of Apple's most loyal markets for YEARS. I think the same applies for video capture cards like the Kona range - what's the use of changing the system if you don't let the third party developers in on it?

Just to confirm you can't use any PCI cards in the mac anymore? Not just PCI-X right?
You are right this is total BS that they got rid of support for PCI.
Now apple goes from being so far behind with single channel DDR1 memory to these stupid so advanced ports I have never heard of any cards coming in PCI express format except video cards. Only high end PC's workstation come with PCI-X nevermind PCI-Express (Other then video) I can't find any PCI Express cards for sale for the mac or the PC (Again other then video cards) What are we suppose to do with all our PCI cards. Nevermind the people who just spent alot of money to buy PCI-X cards, which have only been in mac for what at most 2 years now. Very few motherboards for PC's come with these PCI Express slots (except for the video card slot 16x) and the ones that do only come with one, and they all have at least 2 normal slots PCI or PCI-X (Which are backwards compatable with pci.) Apple basically puts PCI-X out there when most PC manufactors where not using it. (They were the first computer to really use them like the powermac did) and when they came out there were nobody making PCI-X cards for the mac. Now there are a decent number of PCI-X cards available for the mac and Boom now the are useless. Not, to mention I never noticed any card maker that really put out PCI-X cards for under $1000. Except the ones that just added ports like sata-II, Sata-150 and Firewire 800. Now those people have to keep there old macs and connot upgrade, or they have to buy everything new from scratch. Poor marketing on Apples part.
Not to mention the thousands of pci cards out there for the mac that are now useless. I have been waiting for an upgrade for the dual core processors, for a while and now that they come out, I am very dissapointed. I have 3 PCI cards that I use in my powermac that now are useless if I upgrade. I am also dissapointed that only the $3300 model has 4 processors and they only top out at 2.5 GHZ not even the 2.7 that was out before, and basically except for the RAM increases the $2000 model and the $2500 are basically the same if not slower in the processor arena then the prevoious models. I have read in many places on the web that the dual core processors are not as fast as 2 processors. There were no speed bumps just speed descreases in the Quad. Then without any PCI support I might as well buy the old Dual 2.7 which I don't think they even dropped the price on. Which also pisses me off. They could of at least upgraded the Dual 2.7 to DDR2 Memory.
Bottom line is that apple releases what seems to be the greatest Powermac upgrade since they first started using Dual Processors, and they totally alienate all of there existing customers, by abadoning a Powermac standard (PCI) the only mac to even support PCI cards. Then basically creating PCI-X
in there macs allowing people time to buy these cards only to remove it entirely less then 2 years later for this new PCI Express system. Which has basically no third party support. This is poor marketing on apples part. They should of left at least one PCI-X Slot or comeup with an adapter, which is probally not possible. Now you can't buy a new powermac and still use PCI. They do this while people are already hesitant to buy a new mac because of the impending Intel switch.

I am not happy, Bad Steve Jobs Bad Steve.

-Hart

 

[RobHague]

Just like to say i told you so.

Sorry but in another thread (which turned into a mess of PCIe/PCIx and god knows what) i was saying that PCIe, if Apple use it, they will do a total move to it they dont do things by halfs lol. I was just wondering what about PCI-X and the users that need that (or PCI support) seems that their answer to that was to keep the old Dual 2.7Ghz.

Still reckon Dual-Core 2.0/2.3's were about Money saving not performance improvements. Maybe using PCIe cost them less than adding PCI as well as?

Side note-----

I agree with what Harthansen said btw, now you are going to have to wait for PCIe stuff to arrive - but in the mean time Apple are planning on transitioning to Intel anyway. How the heck is that going to work? I mean ok so ATI/NVIDIA and urrr whoever else bring out some nice Mac PCIe products. Wont they need a new BIOS for them to work on the MacTel machines? Does that not mean another Mac PCIe version of the product to work with the x86s that dont exist yet?

Also the great point, what about the PCI cards out there for Mac now? Any new powermacs sold wont be able to make use of them. I bet the manufacturers are not too pleased, they will have to make 2 versions of their cards now to keep Mac users happy. One for PCI (or PCI-X) and one for PCIe (to cover the new systems) and when Intels arrive wont there be BIOS changes so wont that make it 3 versions?

 

[matticus008]

I agree with what Harthansen said btw, now you are going to have to wait for PCIe stuff to arrive - but in the mean time Apple are planning on transitioning to Intel anyway. How the heck is that going to work? I mean ok so ATI/NVIDIA and urrr whoever else bring out some nice Mac PCIe products. Wont they need a new BIOS for them to work on the MacTel machines? Does that not mean another Mac PCIe version of the product to work with the x86s that dont exist yet?

Well, for right now, there are only the existing Mac-compatible video products. The manufacturers might just wait for Intel machines to branch out from there and in the meantime, you can use the (more than adequate) video hardware that comes in the PowerMac itself. You might not have aftermarket upgrades available for a year or two (or you might, since it's not that much work to create a Mac-compatible ROM given the unified driver models graphics cards tend to use). When the Intel machines come out, they will have new graphics cards entirely, so there's no "doubling up" necessary.

Also the great point, what about the PCI cards out there for Mac now? Any new powermacs sold wont be able to make use of them. I bet the manufacturers are not too pleased, they will have to make 2 versions of their cards now to keep Mac users happy. One for PCI (or PCI-X) and one for PCIe (to cover the new systems) and when Intels arrive wont there be BIOS changes so wont that make it 3 versions?

It's not that extreme. Making a PCI and a PCI Express version of the same card is a minor task, since PCIe uses the same driver and system architecture (the OS sees almost no difference). The only difference is in the physical and transport layers, which are handled primarily by the motherboard (and thus the motherboard drivers). It's therefore trivial to offer a PCIe sound card and a matching PCI version, and once the market takes off, that'll be that. It won't matter between PowerPC and Intel, because that only applies to video cards, and none of those are PCI anymore. So there will at most be two different versions for Macs, and the cost and difficulty of doing so will not be that significant.

EDIT: To sum up, PCI Express is most burdensome for motherboard manufacturers (and the people who write chipset drivers for them). The OS publishers and peripheral manufacturers have very little work to do to change over. Peripheral manufacturers have to move the hardware to new boards that fit in the slots and have to include PCIe signaling hardware, but don't necessarily have to redesign their entire product.

 

[osprey76]

One for PCI (or PCI-X) and one for PCIe (to cover the new systems) and when Intels arrive wont there be BIOS changes so wont that make it 3 versions?

If you read the Ars Technica article, there are various methods for regular PCI hardware to work in PCIe systems. Certainly details aren't out just yet, but Apple may have implemented this.

Also, the Intel Macs may not have a BIOS. I'm hoping not as several features will be gone (such as Firewire Target Disk Mode) and BIOS problems will affect Macs (potentially.) Open Firmware is hardware agnostic. IBM used it some of their x86 systems. So, the Developer kits certainly use a BIOS, but shipping Intel Macs may not.